A breaking method and a dicing method are widely used as a method for cutting and chipping a substrate, such as a semiconductor wafer, having electronic elements formed thereon. In the breaking method, after a surface of the substrate is scratched with a diamond tool, a roller is pushed to cut the substrate in a mechanical manner by use of cleavage. In the dicing method, a disk-shaped diamond saw is rotated to cut the substrate. Also in the dicing method where a diamond saw is used, a substrate is given an incision in partway and then cut into chips by breaking, in addition to complete cutting of the substrate.
Additionally, in recent years, a so-called stealth dicing method has been developed in which a laser beam having a permeable wavelength is concentrated by an object lens optical system and is emitted so that the laser beam comes into a focus inside of the substrate, and thereby a region having lower strength than that before the emission is formed inside of the substrate. This method provides an end face having a small edge for cutting and a small amount of chippage. However, in the state where a region having lower strength is formed inside of the substrate, the substrate is not cut but still connected. Accordingly, it is necessary to cut the substrate into chips by breaking.
Patent Literature 1 describes a method for cutting a substrate into chips and an apparatus for this purpose. In this method, (1) in the substrate to be cut, a trench or a processed modified layer serving as a start point of breakdown is formed in advance by laser, scribe, dicer or the like, (2) after adjustment is made so that a blade having an acute tip is brought into contact with the opposite surface of the trench serving as a start point of breakdown, (3) impact force is applied to push the blade into the substrate, and thereby the substrate is cut by breaking.